Industrial processes are known in which web ends must be spliced, for example to attach the leading end of a fresh web to the trailing end of a previously processed web, to join intermediate ends of a web following a break or to join the ends of web to form an endless belt or the shell of a container.
For example, U.S. Pat. No. 766,930 shows a type of splice for an endless belt in which interlocking tongues on the ends of the belt are secured against separation by a glued-on layer of backing fabric. A similar technique is shown in U.S. Pat. No. 1,303,687 for forming the shell of a container. A different technique is shown in commonly assigned U.S. Pat. No. 3,661,667 in which the ends of strips of photographic film are joined by a length of splicing tape which is ultrasonically attached to the ends of the strips. In U.S. Pat. No. 4,445,768 and 4,455,076, the ends of a film strip and a leader strip are overlapped and joined by an undisclosed technique. Strips of pressure sensitive tape also have been used to make such splices.
A difficulty with such known splicing techniques is that a smooth joint is not formed between the ends of the spliced webs. The backing fabric or strip of tape adds substantial additional thickness at the splice, as does the overlap of the ends of the webs. Also, the ends of the backing fabric or strip of tape or the ends of the webs themselves are exposed. This additional thickness and these exposed ends can interfere with downstream web handling equipment. For example, when one of such known types of splices is used to join a leader strip to a length of photographic film, the thick splice or the exposed ends of the backing strip or the webs can snag on portions of the cartridge for the film, on portions of the camera for the film and on portions of the equipment used to process exposed film. Thus, a need has existed for a method for splicing webs which eliminates such additional thickness and exposed ends.